Bore sight



ipr E?, 395i R. s. CQANMER BORE SIGHT Filed Feb. 18, 194'? Invenclr:Rich 1rd 1. Granma? @www www@ E?, R93 R. s. @HAMMER BORE SGHT FiledFeb. 18, 1947 2 Sheetsc-Sheet 2 FE'. J0 J 20 o 46 l 6 4% lliln lf3 Illl" --7 VI l 49 35 2 7 :ij-'E' El- 55 g o 8 l /8 l s /9 /0 /2 Inven'lzclheu-Ef El. Eranmai Patented Apr. 17, 1951 UNITED STATES PATENT OFFICE(Granted under the act of March 3, 1883, as amended April 30, 1928; 3700. G. 757) 3 Claims.

The invention described herein may be manufactured and used by or forthe Government for governmental. purposes without payment of any royaltythereon.

This invention relates to bore sights. Such sights are used to determinethe angular relation between the line of sight determined by the sightsof a gun and the axis of the gun bore. Such sights,uwhen mounted uponthe upper gun carriage or cradle are usually adjustable relatively tothegun to vary the angular relation between the line of sight and thebore axis both in a plane through the bore axis and normal to thetrunnion axis and in a plane parallel to a nor-- mally horizontal planethrough the trunnion axis. Scales are usually provided for determiningthese angular relations and it is important, for angular settingscorresponding to given conditions of. range, windage, etc., that thetrajectory of the projectile intersect the line of sight at the selectedor predetermined range.

Due to various causes such as jump of the gun when fired, subsidence ofthe gunemplacement during firing, and others, the aforesaid relationsare frequently and easily deranged and plug or frame with all partsremoved therefrom.

Referring in detail to the drawings, the numeral I identifies a frame,tampion, or breech plug turned with a slight taper to fit snugly withinthe breech portion of the bore of the gun G, as shown at Fig. 2. Thisframe is recessed for a horizontal slide 6.

one of the prerequisites for a high average of accurate gun fire, isfrequent and precise bore sighting.

way 1.

y A second upper fiat guideway 'I is provided by a block 8 secured bycap screws 9 and I0 to frame I with the elements of guideway 'I parallelto those of 5. The block is guided into proper posiv I1, Fig. 3, to forma clamping face substantially coplanar with the face of guideway 1. Theblock It is therefore an object of my invention to l versely of the boreof any degree within the limits of the instrument to accuratelycompensate for errors in aim that would otherwise be introduced by gunjump, subsidence of the gun emplacement, and other causes.

In the drawing:

Fig. 1 is an elevation of the rear face of the bore sight forming thesubject of my invention showing thesighting element, means for adjusting the same in two mutually normal directions;

together with the scale means for determining the amounts of suchadjustments.

Fig. 2 is a side elevation looking from the right, Fig. 1, and showingthe device in position within the breech portion of a gun bore.

Fig. 3 is a vertical diametrical cross section on a plane indicated byline 3-3, Fig. 1. L

Fig. 4 is a horizontal diametrical cross section taken upon a planeindicated by line 4-4, Fig. 1.

Fig. 5 is a cross section taken upon the line 55, Fig. l, and showingthe construction for detachably mounting one of two opposed guides.

Fig. 6 is a view of the rear face of the breech has a transversedimension less than that of channel I5, and is so proportioned that,when moved to the right, as seen in Fig. 3, its face I'I binds againstthe contiguous face of slide 6 and clamps or confines the latter againstsliding. As best seen in Figs. 3 and 5, clamping movement of block I6,is effected by a shaft I8 journaled in block 8 and threadedly-engagingthe block. The shaft has a reduced outer end forming a shoulder I9abutting against a corresponding shoulder formed by a counterbore inblock 8. A knob 20 is pinned to the reduced end of shaft I8 projectingoutwardly from block .8 so that, as the knob is turned .in onedirection, clamp I6 is forced to the right as s een in Fig. 3, to bindagainst the beveled face of slide 6 and thus clamp the slide in adjustedposition.

From Figs. l, 3 and 6 it will be noted that frame I, has a secondsegment-shaped projection 2 I, recessed as at 22, Fig.,1, to accommodatethe top end of clamp I 6. Projections 4 and 2| may have coplanar outeror 'rear faces, as may be seen from Fig. 3. Lugs 23 and 24 project fromthe face of projection 4: and are formed with aligned apertures 25 and,26 (Figure 6') in which is journaled an adjusting screw 21. Axialmovement of the screw is prevented by a knob 28 pinned to shaft 2l andabutting the adjacent einem inner face of lug 24. A nut 29 is threadedon screw 21 and has a bore at right angles to the axis of screw 21, inwhich a pin smoothly ts.

Pin 3|] is fixed in, and projects from, the lower side of slide 6. Thisslide, as previously implied, has upper and lower dove-tail guidesurfaces tting smoothly between, and guided by the beveled faces 5 and|1 of projection 4 and block 8, respectively. The slide has a relativelylarge, vertically-extending bore 3| spaced from the bottom of the slide,but opening through the top surface thereof, as indicated at 32, Figs. 1and 4, between an upper projection 33 and a lower projection 34, bothformed integrally with the slide. Slide 6 also has a slot shown atFigure 4 below slide and forming a communication between bore 3| and thelower or forward face of the slide. A generally cylindrical verticalslide 35 has a smooth t within bore 3| and is cut away in a planeparallel to its axis, to provide a flat outer face, as indicated at 36,Fig. 4, projecting a little beyond the plane of the.outer face of slide6. A central sighting hole 31 is drilled diametrically through slide 35as well as larger locating holes 38 and 39 on either side of 3l.

Horizontal slide 6 is provided with an upper lug 40 and a lower lug 4l,both extending to the right as seen in Figure l. These lugs arepreferably integral with slide 6, and have aligned holes journaling avertical adjusting screw 42. A nut 43 is threaded on this screw and hasa hole, normal to the axis of screw 42 in which a pin 44 has a smooth t,see Fig. 4. This pin projects with a smooth t through an elongated slotin slide 6, and has a press fit in a radial hole in slide 35. A knob 45is pinned to screw 42 between lugs 4@ and 4| and acts to prevent axialmovement of the screw. By turning this knob the slide 35 may betranslated vertically within and along bore 3|.

- As shown upon Figs. 1 and 4, slide 6 is formed with'a channel 46,normally horizontal and opening into bore 3|. A clamping element 41 hasa loose t within the channel and is formed with a portion of acylindrical surface adapted to be forced into clamping engagement withthe surface of slide S5. Element 41 has a threaded hole engaged by anenlarged threaded portion of a shaft 48. provided by a hole in slide 5,and is prevented from axial movement in one direction by the aforesaidenlarged threaded portion, and in the other direction by a collar 4Spinned to the shaft. The upper end of shaft 48 carries a knob 55 which,on being turned, in one direction, eiects movement of element 41downwardly into clamping engagement with slide 35 to lock the same inadjusted position. A scale plate 5| is attached to the top surface ofslide 6 by screws 52. This plate extends over and across channel 45 andis slotted, as indicated in dotted lines, Fig. l, to clear shaft 4B. Asshown in Fig. 4, slide 35 is grooved to accommodate the adjacent edge ofplate 5|. The latter has a scale 53 graduated in opposite directionsfrom a central zero indication. Slide 35 carries an index 54 in closelyadjacent position for cooperation with scale 53.

As shown in Figure l, a horizontal scale plate 55 is secured by screws56 to the plane outer surface of block 8 and carries a graduated edgeclosely adjacent and in cooperative relation with an index 51'l onslide- 6. Scales 5| and 55v are graduated in mils. l; vv- This shaft isjournaled in a bearing From Fig. 6 it will be noted that the plug l isformed with a central hole 58 as well as four smaller lightening andobservation holes 59. In addition, normally horizontal slots 6U and 6|are provided between each pair of vertically-spaced holes 59. Theseslots are in substantial alignment with peep hole 31 and assist theoperator in initially adjusting the bore sight into a desired relationwith respect to the muzzle cross-wires of well-known construction. Allparts are preferably. of corrosion-resisting metal such as bronze.

In using the device, a distant target is selected or set up at theoptimum range for the gun being bore sighted. A muzzle sight consistingof a frame tting the muzzle portion of the gun bore, is inserted intothe muzzle. This sight provides mutually normal cross-wires extendingdiametrically across the bore. The sight is so positioned that one wireis horizontal. The intersection of such wires locates a point upon theaxis of the gun bore.

The breech sight is then inserted into the breech of the gun and isrotatably adjusted until the aforesaid horizontal wire of the muzzlesight lies along the center of slot-s 6|! and 5| after which the plug ispressed firmly into position. In case the jump value of the gun is knownin terms of horizontal and vertical angular values, the knobs 23 and 55are loosened to free the respective slides, and thumbpiece 28 is turnedto thereby horizontally move slide 6 and all parts carried thereby untilindex 51 indicates the known horizontal jump on scale 55. Knob 25 isthen tightened to lock slide 5 in adjusted position. Thumbpiece 45 isnextturned to move slide 35 vertically until index 54 indicates theknown vertical jump on scale 5|. In each case the adjustment should bein a direction opposite to the direction of jump. For example, if thegun is known to have an elevational increase of 3 mils on firing, thenthe slide 35 should be moved downwardly until a line through peep sight31 and the intersection of the muzzle wires, makes an angle of 3 milswith the bore axis.

Having set the sight as aforesaid, the gun is moved until a line ofsight through aperture 31 and the intersection of the cross-wires at themuzzle, intersects the target. The sights of the gun are now adjustedrelatively to the gun until they too, are directed upon the target. Thiscompletes the adjustment.

In cases where the jump Values of the gun are not known, a target is setup at an optimum ring range. The gun is aimed on the target using ringtable data. If the gun is cold, at least two warm-up shots should befired. Thereafter, at least three more shots are fired and the center ofimpact of the shots upon the target is determined and measured. Thehorizontal and vertical jump are then calculated, using the known rangeof the target.l Thereafter, the sight is adjusted for the horizontal andvertical jump values, in the manner previously described, and aftertraining the bore sight upon the target, the gun sights are alsoadjusted relatively to the gun so that their lines of sight intersectthe target. If check firing shows that a closer setting is required, theforegoing operation can be repeated until the desired accuracy isobtained.

It will thus be noted that I have provided a bore sight that is builtfor rugged service while being relatively simple in construction andhighly accurate in use. Because of the ease with which it may be appliedto a gun and used to correct for jump,the bore'sight forming the subsansaia ject of my invention encourages the frequent checking necessary forsustained accuracy of fire and thus is a decided aid in increasing theaverage accuracy of fire of any gun with which it is used.

While I have shown a preferred form of the invention, varioussubstitutions and alterations will occur to those skilled in the artafter a study of the foregoing disclosure. Hence the disclosure shouldbe taken in an illustrative rather than a limiting sense; and it is mywish to reserve all such changes, modifications and variations as fall.within the scope of the sub-joined claims.

Having now fully disclosed the invention what I claim and desire tosecure by Letters Patent is:

1. A bore sight comprising a frame adapted to engage the walls of and besupported by the breech portion of the bore of a gun, said frame havinga first pair of opposed guideways determining a first path transverselyacross said bore, a rst slide mounted between said guideways fortranslation along said path, a screw journaled on said frame forrotation upon an axis parallel to said first path, a nut threaded uponsaid screw, a pin on said slide fitting a hole in said nut, said rstslide having a second guideway determining a second path normal to saidbore and rst path, a second slide mounted on said first slide fortranslation along said second path, a second screw journaled on saidfirst slide for rotation about an axis parallel to said second path, asecond nut on said second screw, and a pin xed in said second slide andtting a hole in said second nut.

2. A bore sight comprising a tapered plug adapted to t snugly within thebreech portion of thc bore of a gun, said plug having opposed segmentalprojections from one face thereof, undercut to form parallel guidewaysdefining a first path normal to said bore, a slide having opposedprojections tting said guideways, respectively, for translation alongsaid path, a screw journaled on one said projection for rotation on anaxis parallel to said path, a nut threaded on said screw,

a pin xed in said slide and iitting a hole in said nut, there being abore in said slide defining a second path normal to said gun bore andrst path.

3. In a bore sight, a frame having a frustoconical peripheral contourand rst and second opposed segmental projections upstanding from oneface thereof, said rst projection being undercut to provide a firstguideway, a block secured to said frame adjacent said second projectionand being undercut to provide a seco-nd guideway confronting andparallel to said rst guideway, a slide engaging said guideways andguided thereby for translation in a first path transversely of the boreof said gun, a screw journaled in lugs carried by said first projectionfor rotation upon an axis parallel to said path, a nut on said screw, apin secured to said slide and smoothly fitting a bore in said nut, athumbpiece ixed to said screw, and a second slide translatable in andalong a bore in said rst slide, said second slide having a sightingaperture lying on the axis of the bore of said gun when said slides arein central position.

RICHARD S. CRANMER.

REFERENCES CITED The following references are of record in the le ofthis patent:

UNITED STATES PATENTS Number Name Date 37,512 Learock Jan. 27, 1863763,348 Andrews June 28, 1904 793,131 Henkes June 27, 1905 803,435Saegmuller Oct. 31, 1905 1,636,509 Hatcher July 19, 1927 2,294,913Kaufman et al Sept. 8, 1942 FOREIGN PATENTS Number Country Date 307,257Germany Aug. 6, 1918

